Along with the continuous growth of the Internet, various network services appear, and advanced multimedia systems emerge in endlessly. Because real-time services are relatively sensitive to network characteristic such as transmission latency, delay jitter etc., when there are File Transfer Protocol (FTP) services of high burstiness, or Hypertext Transfer Protocol (HTTP) services with image files on the network, the real-time services may be greatly affected. Besides, since multimedia services may occupy much bandwidth, key services, which need to be guaranteed in the existing network, can not be reliably transmitted. Therefore, in order to guarantee reliable transmission of key services, various QoS technologies arise. The Internet Engineering Task Force (IETF) has proposed a good many service models and mechanisms to meet QoS requirement. At present, a scheme, which adopts an Integrated Service (INT-SERV) model on the access or edge area of a network, and adopts a Differentiated Service (DIFF-SERV) model on the core area of the network, is comparatively approved in the art.
In the Diff-serv model, only a measure of setting priority levels is provided to guarantee the QoS. Although this model has a feature of high line efficiency, the real effectiveness is unpredictable. Therefore, an independent bearer control layer is introduced into the Diff-serv Model of the backbone network in the art, a special set of Diff-serv QoS signaling mechanisms are provided, and also a resource management layer is specially established for the Diff-serv network, which is used for managing topology resources of the network. This Diff-serv mode of resource management is called a Diff-serv model with an independent bearer control layer. FIG. 1 is a schematic diagram of the model. Here, the 101 is a service server, such as a Call Agent (CA), which belongs to the service control layer for implementing functions such as soft switch; the 102 is a bearer network resource manager, which belongs to the bearer control layer; the 103 is an Edge Router (ER) and the 104 is a Core Router, both of which belong to the bearer network. In this model, the bearer network resource manager is responsible for configuring management policies and network topology, allocating resources for service bandwidth applications of customers. The service bandwidth application requests and results of customers, and the path information of service applications, etc., which are allocated by every bearer network resource manager, are delivered via signaling between bearer network resource managers of each control domain.
When processing a service bandwidth application request from a user, the bearer control layer will assign a path for the service, and then the bearer network resource manager will inform the ER to forward the service stream according to the assigned path. How could the bearer layer transfer the service stream with reference to the path assigned by the bearer control layer? At present, an existing approach in the art is to use the Multi-protocol Label Switching (MPLS) technique, and with a resource reservation mode, establishing a Label Switched Path (LSP) along the service stream path assigned by the bearer control layer, where the end-to-end LSP is set up by using explicit route mechanisms, such as the Resource Reservation Protocol-traffic engineering (RSVP-TE) or the constraint-based routed Label Switched Path (CR-LDP).
In a multi-layer network structure, especially when the control layer and the bearer layer are separated, the procedure for establishing a session connection includes: interaction between service control layer entities, interaction between bearer control layer entities, interaction between service control layer entities and bearer control layer entities, and interaction between bearer control layer entities and bearer layer entities. Every entity involved may keep information related to the session connection, for example, the service control layer may reserve session establishment information, the bearer control layer may preserve session resource establishment information, and a bearer layer entity may preserve policy information of session data flow. All the information should be consistent. When certain node equipment is abnormal during information processing procedure, such as resource releasing, the information on the network will be inconsistent. In this case, resources allocated by some nodes for the session connection, including memories, buffers and bandwidth etc, cannot be released in time, and thus, the resources may be hung up.
At present, cold backup is one of the simplest methods to guarantee service reliability, which means using one entity as a complete backup of another entity. For example, entity B is taken as a backup entity of entity A, and when entity A fails, the backup entity B will totally substitute for entity A. Nevertheless, for the backup entity B, a premise to totally substitute for entity A is to rebuild both the bearer connection and the service connection. The cold backup method is the most effective routing mechanism and easy to implement in the initial stage of network construction, because at this stage the network is small, the real-time requirement for service is not critical, and switching and smoothing are not needed, as well. Therefore, the cold backup method is competent in the case when traffic volume is low, and interruption is allowed. However, along with the growth of traffic volume, and the expanding of real-time services, which are not expected by users to be interrupted, the deficiency of cold backup method appears gradually. That is, in the face of this situation, a device failure may occur, and services should be interrupted and rebuilt. Thus, if the cold backup method is adopted in a wide area network which is complex and of critical real-time requirement, services will be interrupted and rebuilt when a certain section of bearer network fails.